I have a Drobo 5N running Mavericks (previously Mountain Lion) and I continue to have the same concern: when the Drobo becomes full, will time Machine recognize that the drive is effectively “full” and start deleting old backups to create space for new ones or will I have to create an entirely new backup of terabytes of data, effectively starting all over again?
You have to configure the Time Machine share with a specific quota; when it reaches that amount it will be detected as full and Time Machine will do its auto-deletion thing (this also keeps Time Machine from eating all of space on your Drobo). If you don’t do this, then no, it will never realize the volume is full, as the magic of Thin Provisioning will make it appear as if it always has space (well, up to a 16TB volume size).
Thanks so much for the info!
My question then is that will I basically have the Drobo “critically low on capacity” with a red light?
It’s funny, but I just looked at the backup and it appears that it is in the “Cleaning up old backups” state, so I think that means it is deleting the oldest backups to make space for the newest, right? I knot the old software got really confused by Time Machine.
If you have a 5-bay Drobo with 5 x 3TB drives. That gives you 10.9TB for data storage. When you setup the box for Time Machines, you create a share and assign a quota to that share - let’s say 2TB. As far as your Mac client is concerned that share has just 2TB on it, regardless of how much space from the 10.9TB is actually free. So when your backups reach the 2TB limit, Time Machine on the Mac will start deleting old backups to free up space - even if there is way more free space on the Drobo, because you have told Time Machine it can only have 2TB from the 10.9TB total. It knowns nothing of the other space available. If you only have, for example 1TB of backups then Time Machine on the Mac will see 1TB of free space. As long as the Drobo itself has more than 1TB free then all is good.
What I honestly don’t know is what would happen if your machine had less free space overall than the Time Machine enabled share was reporting back to the Mac client.
Once you set aside a certain amount of space for Time Machine, the Drobo won’t let something else use it, and I don’t believe it will allow a Time Machine quota larger than the diskpack, so you never have to worry about the Drobo not having space to fill the quota.
(just make sure you do limit timemachine to an amount of real space you have free, otherwise it could try to eat up more space than the drobo and cause problems)
Does anyone know, the best way to expand the Time Machine partition on a Drobo when additional disk space is added?
I have been using the Drobo 5D with 4 x 4TB drives, and have just added an additional 4 TB drive. At the moment my Drobo has two partitions one which I use for Time Machine backups and a second that I use as ‘additional storage’.
I was advised by Drobo tech support to use maximum 85% of the Drobo capacity with Time Machine, which I have done and have experienced no problems.
Now I have added the final 4TB drive I would like to expand the Time Machine partition without losing any data.
Has anybody done this, and could they suggest a step-by-step guide.
Thanks in advance,
Michael.
Currently there is no way to expand the time machine partition, you would need to create a new volume enabled for time machine support, and enter in the larger size you would like to use. Currently Drobo does not support resizing volumes, which is why we recommend setting it to the largest size you anticipate you will need. If you do need to expand the volume, the only work around is to create a new volume the correct size and copy all the data over to the new volume so that you can delete the old volume.
Kind Regards,
Drobo Support
I have had frankly a frustrating experience with my 2nd Gen Drobo from day one with Time Machine, and this is my biggest beef. The perpetual filling without auto-deletion. The sharing process above is genius. What I don’t understand is how to do this. Hoping someone can provide instructions.
Thanks.
hi jay, as far as i understand it, the newer models of drobo (after gen1 and gen2), support a new volume for backups such as timemachine here:
https://myproducts.drobo.com/article/AA-01862
there seems to be a method for older models, such as gen2 which is here:
https://myproducts.drobo.com/article/AA-01809
(but please read all the info and probably good to make backups elsewhere first if possible, based on what it says)
alternatively, there is a very good guide johnm posted here which is worth reading up too, as there might be a way to simply create a new virtual flat file instead of formatting new drobo volumes:
http://www.drobospace.com/forums/showthread.php?tid=143858
(ideally, time machine would simply provide a config setting, so that users can say "back-up up to this line, and no further) 
[quote=“Paul, post:10, topic:139393”]…(ideally, time machine would simply provide a config setting, so that users can say "back-up up to this line, and no further)
[/quote]
Thanks for the links, Paul. I’ll check those out.
You couldn’t be more right about the ability (or lack thereof) to set a limit on Time Machine’s backup range. Ridiculous that after all this time such a simple thing hasn’t been implemented.
ok sure - hopefully they can help a bit, (and for the timemachine ability, if its not there in the code yet then it might just be a case of innovation or simplification vs procrastination) 
I have just hit the wall with Time Machine on my Drobo 5D. I had set up this Drobo as dedicated to backups, and pointed Time Machine to it. I also put a few other archive files on it.
When I got the red alert “Drobo is critically low on capacity” message I moved out some of the other large files. To my dismay the full condition persists.
While exploring Drobo Dashboard I discovered the facility for creating a fixed-size partition for Time Machine. That is great, but how do I get there from here?
Do I have to throw away my existing Time Machine archive, reformat the Drobo, create the partition and start over? Is there any way to save my existing backups?
I have a second backup off-site with CrashPlan, so saving the Time Machine archive isn’t critical, it would just be convenient.
hi dandugan,
am not sure if you saw the links on the 1st page, though i think there is a way to move a previously created time machine backup. that pondini site might have the info too, though it might need to be carried out in a certain way with command lines but i do not have a mac to know for sure. If you are low on space currently though, then i think you still need to copy the time machine backup files onto another, separate drive (such as the internal computer drive or another external drive with a similar filesystem), and then to essentially move it there once happy with the command or procedure, and then to copy it back onto the new, time machine area.
maybe while you wait for confirmation, you could start finding a drive to copy to in the meantime?